Summary of the Museum Preservation Environment Summit

Smithsonian LogoOver 250 people attended the Smithsonian institution Summit on the Museum Preservation Environment held at the National Museum of the American Indian on March 5th. Many more were able to view the entire summit on the web. If you missed this important presentation, it is available for viewing at: The goal of the summit was to provide Smithsonian Institution staff with information on the role of environment in preserving collections as they move away from commonly accepted environmental “standards” and develop a pan-institutional declaration on environmental controls for collection areas that will guide future environmental management policies.

Based on IPI’s extensive research on preservation environments for cultural heritage collections, IPI Director Jim Reilly was invited to be one of seven speakers at the summit, presenting “Standards and Best Practices, Part I: Choosing Standards and Best Practices.” Jim’s talk reiterated themes common to the summit. Primary among them, the environmental “ideal” that most preservation professionals are familiar with—70°F +/- 2° and 50% RH +/- 5%—is an oversimplification of original research on the effect of environment on collections, and disregards much of the research done in the last 30 years or more. Reilly’s talk emphasized the importance of understanding the vulnerabilities of the collection, the nature of the climate, the building envelope, and the mechanical system, while at the same time stressing the importance of sustainable operation of HVAC systems.

Stefan Michalski, Senior Conservation Scientist, Canadian Conservation Institute, pointed out the decades-long history of ignoring both the limitations and broader recommendations of the research into environmental management for preservation. Recommendations made as early as the 1930’s by staff at the Tate Gallery were based specifically on the needs of painting collections, London’s climate, and the environment that the building and its mechanical system were capable of maintaining in the summer (55% - 60% RH). In reality, many of the research studies that Michalski cited recommended that collecting institutions deal with the extremes of RH (periods of extreme dampness and dryness), allow different bands of RH fluctuation for different collection types (45% to 65% RH for most materials), and seasonal mechanical system adjustments for most climates. In many instances scientists were persuaded to present the field with easy to remember numbers rather than a formulation that took a little more work to understand.

Both Michalski and Reilly referenced Garry Thompson, author of “The Museum Environment,” first published in 1978, and revised in 1986. Thompson is considered by many to be the source of the “70/50” standard and a leader in the field. However, Thompson did qualify the suggested temperature and RH levels in several ways. He called for continued investigation of material behavior to more realistically set environmental limits. He acknowledged taking the limitations of mechanical systems and the need for human comfort into consideration, and he recommended seasonal variation. What he actually said was:


70/50 ZombieTemperature recommendations

  • Winter - 19 ºC +/- 1º (67ºF +/- 2º)
  • Summer - up to 24 ºC +/- 1º (75 ºF +/- 2º)
  • Note 1: Temperature must be controlled to control RH, but the level is dictated by human comfort. For fuel economy, different summer and winter levels are suggested.
  • Note 2: In storage areas or buildings closed to the public in winter, temperatures can be allowed to fall, but not to the point where condensation may occur on cold or unventilated surfaces. A lower limit of 10 ºC (50 ºF) is suggested.


Relative Humidity recommendation

  • 50% or 55% RH +/- 5%, day and night throughout the year.
  • Note 1: The level may be fixed higher or lower, but for mixed collections should be in the 45 ~ 60% range.
  • Note 2: Special exhibits may require special conditions.

Thompson also noted that “the standard specification of +/- 4 or 5% in RH control is based more on what we can reasonably expect the equipment to do than on any deep knowledge of the effect of small variations on the exhibit.” (Second edition, 1986, p.118)

To steal a quote from Jim Reilly’s presentation, "it’s time to put a stake in the heart of the zombie of 70/50" for all collections, all the time. The standard is not ideal for all circumstances, doesn’t meet the needs of many collection types, and is difficult and costly to maintain mechanically.

The reality is that there is no such thing as a “one size fits all” or “straight line” environmental standard that is easily attainable, appropriate for preservation of mixed collections, or environmentally sustainable. Collection care staff must develop a risk-managed approach based on the most significant vulnerabilities of collection materials, the local climate, the capabilities of the mechanical system, and the limitations imposed by the building’s construction. To be effective, this should be a team approach, including collection care and facility management, driven by reliable environmental data.

This environmental management approach was emphasized by R. Robert Waller, Protect Heritage Corp., who spoke about “Risk Assessment and Assignment of Environment Parameters.” Waller outlined a risk-based and well-documented process for environmental management that requires informed decision making and takes the perspectives of several key players in facility management, collection care, and conservation science into account.


It’s time to embrace new standards and best practices, based on decades of research as well as the reality of environmental change and the need for sustainable practices.


Michael Henry, Watson & Henry Associates, covered environmental change and sustainability in his presentation on “Conservation Environments, Museum Buildings, and Sustainability.” He noted that the interior environment is driven by thermal energy and moisture – and of the two, moisture is the most critical. He quoted Jim Reilly’s statement that “geography is preservation destiny” illustrated by this map of climate zones in the US.


Climate Zones of the Continental United States


From west to east in the USA, the environment moves from marine to dry to moist climates, and from north to south, cold to warm to hot conditions. The outdoor environment, the building envelope, and the capabilities of the mechanical system all have to be taken into consideration to determine the optimal environment. The reality is that mechanical systems are configured to human comfort, which means that temperature control is easy and moisture control is not. In an ideal situation, collection storage should be segregated from occupied areas including offices, cafes, theaters, etc. Human comfort conditions don’t meet the needs of collections. Henry too made the point that defining the best environment for a given institution requires a collaborative effort between collections and facilities staff.

A risk-managed, holistic approach to environmental management was also reflected in the presentation by Jonathan Ashley-Smith which discussed the British Publicly Available Specification, or PAS 198: 2012. This publication detailing “Specifications for Managing Environmental Conditions for Cultural Collections” was published by the British Standards Institution to help collecting institutions establish and maintain environmental conditions that preserve cultural collections in their care. No “ideal” standard is presented—the goal is to help users make their own judgments based on local climates, an understanding of collection material vulnerabilities to agents of deterioration, and the move toward energy reduction. The introduction makes that point that “There is general agreement that it is time to shift museums’ policies for environmental control, loan conditions and the guidance given to architects and engineers from the prescription of close control of ambient conditions throughout buildings and exhibition galleries to a more mutual understanding of the real conservation needs of different categories of object, which have widely different requirements and may have been exposed to very different environmental conditions in the past.”

PAS 198: 2012 is available for purchase at provides valuable information on managing the environment for preservation, temperature, relative humidity, light, and pollution. PAS 198: 2012 includes decision making guidelines in the form of tables which illustrate the relative risk of damage and deterioration for various modes of decay. This allows users to choose from a continuum of preservation quality, decay risk (based on collection sensitivities), and energy savings. Ashley-Smith showed the PAS 198 Annex D table below noting that RH affects materials vulnerable to various types of decay in different ways.

Risk-based collection management guidelines are also available from The Canadian Conservation Institute at



The March 5th Summit on the Museum Preservation Environment successfully presented an overview of the development of environmental standards, and current guidelines and best practices, all of which are in line with IPI’s research, tools, publications, and presentations on environmental management:

  • Environmental control is fundamental to collections preservation
  • Best practices must be based on a number of factors including:
    • Evolving material-specific environmental standards
    • Building fabric and mechanical system capability
    • Available staff and resources, and
    • The growing impetus to reduce energy costs
  • A collaborative approach involving a cross functional team of facilities, collection care and administrative staff is key
  • Environmental monitoring and data analysis is essential, and
  • The process of managing the environment for preservation is ongoing